Nutritional Profile and Antibacterial Activity of the Black Soldier Fly (Hermetia illucens) Larvae Meal as Potential Protein Source for Aquafeeds

The black soldier fly (BSF, Hermetia illucens) is a well-known insect with promising potential in transforming organic wastes into protein-rich biomass. The BSF larvae (BSFL) can replace expensive sources of protein used in aquaculture and have antimicrobial characteristics that are recognized to inhibit pathogenic bacteria in humans, plants, poultry, and livestock. However, its potential against pathogenic bacteria in aquaculture remains largely unexplored. To address this gap, BSFL in different instar stages were analyzed for their proximate, mineral, and fatty acid contents to determine their nutritional composition. Additionally, disk diffusion and minimum inhibitory concentration assays were used to evaluate the antibacterial activity of the crude methanolic extracts of the BSFL against Aeromonas veronii, Edwardsiella tarda, Streptococcus agalactiae, and Vibrio harveyi. Results showed high nutritional composition across instar stages but the highest level was revealed in 2- and 3-instar stages (crude protein: 36.17, 36.96%, and crude fat: 33.84, 40.90%, respectively). Crude methanolic extract of BSFL inhibited the growth and proliferation of all tested bacteria, with the highest inhibition observed in Streptococcus agalactiae. Moreover, the extracts obtained at 5-instar exhibited the highest antibacterial activity compared to other extracts. This study showed that the BSFL have the potential to serve as a sustainable protein source in aquafeeds, and the crude methanolic extracts from later-stage BSFL can be used as antibacterial agents in aquaculture.